Effect of laser pulses on the surface and structural modification of ablated titanium in a liquid-confined environment

Abstract

The effect of laser pulses on surface morphology, chemical composition and crystallinity of titanium samples after irradiation in ethanol environment has been investigated. KrF Excimer laser (248 nm, 20 ns and 20 Hz) was employed for this purpose. Targets were exposed for various number of laser pulses ranging from 500 to 2000 in ambient environment of ethanol at a fluence of 3.6 J/cm2. In order to explore the modification in surface morphology, chemical composition and crystallinity, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) techniques were employed, respectively. SEM analysis reveals the formation of grains. The grain size initially decreases for increasing number of laser pulses up to 1500 and then increases with further increase in number of laser pulses up to 2000. The grain boundaries become diffused with increase in number of laser pulses from 500 to 1500. Further increase in number of pulses, up to 2000, results in much wider and distinct grain boundaries. At peripheral ablated areas, small-sized diffused grains are revealed. EDS analysis reveals an increase in the content of oxygen up to 29.25 wt.% at the central ablated area. Whereas the value of oxygen content increased to 33.08 wt.% in the peripheral ablated area, which caused the decrease in the grain size as observed in the SEM results of the peripheral ablated area. XRD analysis reveals the formation of titanium hydride along with the development of various phases of titanium oxide (Rutile: TiO2). For various number of laser pulses, the variation in the peak intensity, crystallinity and d-spacing is observed for irradiated titanium.